1. Field of the Invention
This invention relates to a stamped and formed electrical contact terminal for establishing an insulation displacement contact with an insulated wire. More specifically, this invention relates to a terminal for establishing an interconnection between an insulated wire and a pin, such as a pin on a printed circuit board. Still more specifically, this invention relates to a stamped and formed electrical contact terminal in which an insulation displacement contact is formed by inserting an insulated conductor into a plate having a slot extending inwardly from one end, in which sidewalls of the terminal extend transversely past opposite edges of the plates.
2. Description of the Prior Art
Insulation displacement interconnections between insulated conductors and terminals using slotted plates have proven quite effective in establishing low cost electrical terminations. U.S. Pat. No. 3,767,841 discloses one electrical connector employing slotted plates folded upwardly form the base to form a "U" shaped contact member. The edges of the slot formed in the two plates in this terminal penetrate the insulation surrounding the inner conductive core and establish a secure, gas-tight interconnection to the underlying conductive core. Contact is established by the use of multiple slotted plates.
The connector shown in U.S. Pat. No. 3,767,841 is a splice connector in which two or more wires are terminated to the same connector in one operation. This same slotted plate insulation displacement concept has been expanded to permit a large number of wires to be attached to separate terminals in a single insulative housing, all at the same time. This concept is generally referred to as mass termination.
U.S. Pat. No. 3,926,498 discloses a number of terminal configurations each of which can be positioned within a single insulative housing for mass termination. These terminals generally employ slotted plates which are either folded inwardly from side edges of a "U" shaped channel of a stamped and formed terminal, or are folded upwardly from the base of the channel shaped terminals, between opposed sidewalls. The various embodiments of the contact terminal shown in U.S. Pat. No. 3,926,498 all disclose versions in which the slotted plates engage the sidewalls of the contacts. In these versions of contact terminals, ears are formed on the side edges of the slotted plates, and these slotted plates fit within cut-outs or slots located on the exterior of the sidewalls. A slotted plate supported in this manner by a "U" shaped member does not tend to collapse when a wire is inserted laterally in its axis into the slot. Contact terminals which use a "U" shaped member in which the slotted plates formed upwardly from the base of the "U" are held in engagement by sidewalls extending from the opposed edges of the base are also shown in PCT International Application WO No. 86/01941; U.S. Pat. No. 4,545,634 and in Japanese UM Publication No. 60-142463.
As insulation displacement terminals, of smaller and smaller sizes are employed, it becomes more and more difficult to form this attachment between the slotted plates and the opposed sidewalls. One problem is that as the terminals become smaller and smaller, the size of the punched openings formed by removal of material become smaller. It also becomes more difficult to form precise shear lines. It becomes more and more difficult to form narrow openings because such openings must be formed by a protruding die blade which is no thicker than the width of the slot. Excessive die wear would then become a problem.
Not only does it become more and more difficult to stamp and form these smaller terminals but performance limitations can also become quite critical for small contact terminals carrying relatively high current. For example, any material which is stamped out of a terminal of this type reduces the cross sectional area available to carry current. Furthermore, any material which is eliminated also reduces the surface area of the contact, thus reducing its ability to dissipate heat formed by the current passing through the terminal. Furthermore, any elimination of material also reduces the mechanical strength of such a terminal.